The invention belongs to the field of plate processing, and particularly relates to a plate side wall grinding device. The device comprises a workbench, two supporting plates are fixedly connected to the workbench, pull rods are slidably connected to the supporting plates, grinding blocks are fixedly connected to the pull rods, and reset springs are fixedly connected between the grinding blocks and the supporting plates. The pull rods are sleeved with the reset springs, a cavity is formed in the workbench, and a first rotating shaft and two second rotating shafts are rotationally connected in the cavity. According to the plate side wall grinding device, through the arrangement of a lead screw and a sliding plate, the lead screw can be controlled to rotate, so that the sliding plate slides downwards, suction cups form negative pressure, a circular plate is sucked, the placement stability of the circular plate is kept, and the tedious operation of manual supporting is avoided; and in addition, through cooperation of a driving motor and the grinding blocks, the circular plate can be fully ground by the grinding blocks in the rotating process, and labor loss of manual grinding is avoided.